Accelerometers are sometimes incorporated into electronic devices such as handheld electronic devices to provide a variety of functions including, but not limited to, determining the position (e.g. tilt or orientation) of the device and detecting a tap on a touchscreen device. Assembling accelerometers into electronic devices typically requires accelerometer calibration issues to be addressed. Although calibration of accelerometers has largely been a factory test problem following their manufacture, the assembly of accelerometers into electronic devices may result in accelerometers that are rotated or tilted relative to the desired position. That is, the accelerometer may suffer from non-zero pitch and roll effects. Furthermore, after a power cycle in which the electronic device is turned off and then on, some of the operating characteristics of the accelerometer may change. Accordingly, in at least some instances it may be desirable to calibrate or recalibrate the accelerometer after the accelerometer is assembled into the electronic device.
The use of accelerometers for inertial navigation systems (INS) and other high resolution/high accuracy applications (such as, for example, motion detection systems in wireless game controllers) requires more precise calibration of accelerometers. Automated calibration systems may be expensive and the time required to calibrate the accelerometer (either manually or automatically) adds to the total cost of production of the electronic device. This is a particular concern in the context of high-volume manufacturing of electronic devices having a built-in accelerometer.
Thus, there remains a need for improved methods of calibrating an accelerometer.
Like reference numerals are used in the drawings to denote like elements and features.